1. Field of the Invention
The present invention relates to a motion adaptive YC separation apparatus for separating a luminance signal (hereinafter referred to as Y-signal or simply as Y) and a color signal (hereinafter referred to as C signal or simply as C) from a composite television signal (hereinafter referred to as V-signals) in which the color signal is frequency multiplexed on the high frequency area of the luminance signal, and more specifically, to a motion detecting apparatus suitable for detecting the motion in a motion adaptive scan-line interpolating apparatus for converting the television signal from interlace scan to sequential scan.
2. Description of the Related Art
Many improvements have been made for a motion adaptive process aiming at improvement of picture quality on the current color television. The motion adaptive process means a process to detect the motion of the picture locally by the motion detecting circuit and to switch-over between the still picture process that is suitable for the still picture and the moving picture process that is suitable for the moving picture adaptationally according to detected motions. The primary motion adaptive process in the current color television includes a motion adaptive YC separation process and a motion adaptive scan-line interpolation, and various signal process circuits for improving the picture quality by the use of a delay circuit having a delay time that is the same as the vertical scanning frequency of the television signal or higher (hereinafter simply referred to as delay circuit) has been proposed with the development of the mass storage digital memory.
In some of video signals that are transmitted or accumulated in the form of three system component signal including a luminance signal and two types of color difference signals used in, for example, a digital television broadcast or in consumer-oriented DVD players and that employ interlace scanning, a signal processing circuit that performs motion adaptive scan-line interpolation is used as described above.
In addition, when displaying a television signal of interlace scanning on the display device of dot matrix type such as a liquid crystal panel or a plasma display, there are cases where the signal processing circuit that performs motion adaptive scan-line interpolation is used.
The motion adaptive YC separation process removes the cross component elements such as cross color or dot scroll completely by separating Y signal by taking sum of the frames and C signal by taking difference between the frames when it is determined to be a still picture in accordance with the amount of the motion detected by the motion detecting circuit. When it is determined to be a moving picture, Y signal and C signal are separated by intra-field process.
The motion adaptive scan-line interpolating process performs the inter-field interpolation to remove line flickers when it is determined to be a still picture according to the amount of motion detected by the motion detecting circuit in the same manner as described above, for the purpose of converting interlace signal to sequential scan signal. When it is determined to be a moving picture, inter-field interpolation is performed.
The accuracy of motion detection of the motion detecting circuit in the above-described motion adaptive process has a significant effect on the quality of reproduced picture. The error in motion detection may be classified into two types as follows.
(1) Detection Error: a part of a still picture is determined to be a moving picture and moving picture process is performed.
(2) Detection failure: a part of a moving picture is determined to be a still picture and still picture process is performed.
Out of these two types of errors, xe2x80x9cDetection failurexe2x80x9d deteriorates the picture quality significantly, and thus the motion detecting circuit that prevents detection failures as much as possible has been proposed.
FIG. 9 is a block circuit diagram showing an example of the motion detecting circuit in the related art shown in Japanese Patent Laid-Open No. 90987/1988. This example is based on the premise that input signal is V-signal.
In FIG. 9, NTSC (National Television System Committee) system analogue V-signal incoming through the input terminal 1 is converted into a digital signal at analogue/digital conversion circuit (hereinafter referred to as ADC) 2. The digitized V-signal is fed to the first detecting circuit 3 to detect the motion of the Y-signal low frequency component. In the first detecting circuit 3, digitized V-signal is fed to the first frame memory 4 and then a signal delayed by one frame and a signal fed into the frame memory 4 are supplied to the subtraction circuit 5 to obtain a difference signal across one frame. Then, the output signal from the subtraction circuit 5 is fed to the low-pass filter (hereinafter referred o as LPF) 6 to remove the color signal band, so that motion information of Y-signal low pass component can be obtained in the output of LPF 6. At this time, it is determined to be a still picture when the output of LPF 6 is zero, and to be a moving picture when the output is the value other than zero. The output signal of LPF 6 has polarities of plus and minus, it is fed to the absolute value circuit 7 to obtain an absolute value. The output of the absolute value 7 is a conversion circuit 8, and is converted into non-linear shape by the I/O characteristics as shown in FIG. 10, and input of low level is converted into the output of zero to remove the noise effect.
On the other hand, a digitized V-signal from ADC 2 is fed to the band-pass filter (hereinafter referred to as BPF) 9 to obtain a signal in color signal band. By the action of ACC operated so as to maintain the level of burst signal contained in the output signal of BPF 9 constant, the output of the amplification circuit 10 for ACC contains a constant signal in which the variation of color signal level caused by the frequency characteristics of the transmission path is corrected. Thereafter, the color signal is demodulated by demodulation circuit 11, which works to cancel the inversion of the phase of the color width carrier between frames. The output of the demodulation circuit 11 is fed to the second detecting circuit 12 to detect the motion of the signal in the color signal band.
In the first place, the output signal of the modulation circuit 11 is fed to the second frame memory 13 to delay by one frame, and then fed to the third frame memory 14 to delay by another frame. Then, the output signal of the demodulation circuit 11 and the signal delayed by two frames by the frame memories 13 and 14 are fed to the subtraction circuit 15 to obtain the difference signal across two frames. Two signals two frames away from each other are identical in the phase of high frequency components of Y-signal and C-signal. In the case of a still picture, the difference across two frames is zero, and thus when the difference signal across two frames is a value other than zero, it is determined to be a moving picture. Moreover, the absolute value circuit 16 and the conversion circuit 17 operate in the same manner as the absolute circuit 7 and the conversion circuit 8 respectively.
The output signals of the first detecting circuit 3 and of the second detecting circuit 12 described above are combined by feeding them to the combining circuit 18. Thereby, the output of the combining circuit 18 contains motion information of signals across the whole band of V-signal. The combining circuit 18 can be implemented by selecting a lager signal out of two input signals.
By feeding the output signal of the combining circuit 18 into the spatio-temporal filter circuit 19 and using motion information of certain pixels being spatio-temporally around a certain pixel together, erroneous detection of rapid motion of the object is prevented. In the spatio-temporal filter circuit 19, the output signal of the combining circuit 18 and the output of the spatio-temporal filter circuit 19 are multiplied by xcex1 (0 less than xcex1 less than 1) in the coefficient circuit 20, and then the maximum value of signals delayed by 262 H period and 263 H period is obtained by the field memory 21 and the line memory 22 in the maximum value circuit 23, and then the filtering process in the horizontal direction is carried out by the horizontal filter circuit 24. With this procedure, vertical and horizontal motion information of a certain pixel and motion information of the past pixel can be referenced. Since the spatio-temporal filter circuit of this example is a feedback type, motion information of the pixel in the range determined by the coefficient xcex1 can be referenced. For example, when xcex1 is closer to 1, the range that can reference is wide and when xcex1 is closer to zero, that range becomes narrower.
In this example, the motion of the signal across the whole band of V-signal is obtained by combining the output of the first detecting circuit 3 and the output of the second detecting circuit 12 in the combining circuit 18. In addition, the erroneous detection of the rapid motion of the object is prevented by filtering motion information in the spatio-temporal filter circuit 19. The motion of the picture is detected with high accuracy in this way.
The motion detecting apparatus of the related art is constructed in such a manner that the motion of the picture is detected by the first detecting circuit for detecting motion of the picture based on the lower frequency component in the difference signal across one frame of V-signal and the second detecting circuit based on the difference signal across two frames, and the output signals from said two detecting circuits is combined, and then the filtering process is carried out by means of spatio-temporal filtering circuit employing a field memory.
In this arrangement, there are recognized disadvantages in that when a scene including characters or fine pictures or patterns are taken by a handy camera, slight shaking of camera at the time of shooting causes a still picture to be determined as if it is partially a moving picture, and in addition, a filtering process by the spatio-temporal filter circuit makes the erroneous motion detection spread over the temporal space.
With such circumstances in view, it is an object of the present invention to provide a detecting apparatus in which motion information of the signal across the whole band of V-signal is detected and the picture of rapid motion is also detected accurately, and when the erroneous detection is made locally, motion of the picture can be detected accurately without unnaturalness by eliminating the effect of the filtering process performed by the spatio-temporal filter circuit. It is another object of the invention to provide a motion detecting apparatus for achieving the same effect also for a component signal across the whole band.
The motion detecting apparatus according to the first invention comprises: a motion detecting circuit for detecting the motion of the picture signals according to the differential across at least one frame; a vertical edge detecting circuit for detecting slow motion of the vertical profile of the picture signals in the horizontal direction; a horizontal edge detecting circuit for detecting slow motion of the horizontal profile of the picture signals in the vertical direction; a motion information detecting circuit for obtaining motion information of the picture from the output of said vertical edge detecting circuit, the output of said horizontal edge detecting circuit, and the output of said motion detecting circuit; a compensation circuit for compensating the rapid motion in motion information supplied from the motion information detecting circuit; and a motion information correction circuit for correcting motion information of each pixel in the picture signals obtained from the output of said compensation circuit by motion information of peripheral pixels.
A motion detecting apparatus according to the second invention provides a motion detecting apparatus as set forth in the first invention, characterized in that the vertical edge detecting circuit detects the motion of the picture signals according to the amount of amplitude of the vertical high-pass component and the correlation amount of horizontal-temporal of the high-pass component.
A motion detecting apparatus according to the third invention provides a motion detecting apparatus as set forth in the first invention, characterized in that the horizontal edge detecting circuit detects the motion of the picture signals according to the amount of amplitude of horizontal high-pass component and the correlation amount of vertical-temporal of the horizontal high-pass component.
A motion detecting apparatus according to the fourth invention provides a motion detecting apparatus as set forth in the first invention, characterized in that the motion information correction circuit corrects the amount of the motion of the pixel of interest in the picture signal according to the amount of the motion of the pixels in the proximity thereof.
A motion detecting apparatus according to the fifth invention provides a motion detecting apparatus as set forth in the first invention, characterized in that the motion information correcting circuit detects the moving picture pixels and the still picture pixels from the pixel of interest to be processed and the peripheral pixels, and corrects the motion information of said pixel of interest according to the number of the pixels of the moving picture, or of the still picture.
A motion detecting apparatus according to the sixth invention provides a motion detecting apparatus as set forth in the fifth invention, characterized in that the motion information correcting circuit performs at least a plurality of times of addition or subtraction of a prescribed amount of motion to or from said motion information of the pixel of interest according to the number of pixels for moving picture detected from the pixels of interest to be processed and the peripheral pixels thereof.
A motion detecting apparatus according to the seventh invention provides a motion detecting apparatus as set forth in the fifth invention, characterized in that the motion information correcting circuit performs at least a plurality of times of addition or subtraction of a prescribed amount of motion to or from said motion information of the pixel of interest according to the number of pixels for moving picture detected from the pixels of interest to be processed and the peripheral pixels thereof.